llvm获取注释

Question

我在新表格下更新了我之前的问题。大家好，

我有以下LLVM IR：

@.str = private unnamed_addr constant [3 x i8] c"DS\00", section "llvm.metadata"

@llvm.global.annotations = appending global [1 x { i8*, i8*, i8*, i32 }] [{ i8*, i8*, i8*, i32 } { i8* bitcast (i32* @f to i8*), i8* getelementptr inbounds ([3 x i8]* @.str, i32 0, i32 0), i8* getelementptr inbounds ([9 x i8]* @.str1, i32 0, i32 0), i32 18 }], section "llvm.metadata"

我需要得到@f（或者我可以以某种方式获得@f = global i32 0, align 4的定义）而且我需要从@.str获得“DS”。在我的目标代码中，我有：

__attribute__((annotate("DS"))) int f=0;

我有问题解析@ llvm.global.annotations，我假设我将使用@ .str。我尝试了什么：

1.

for (Module::global_iterator I = F.global_begin(), E = F.global_end(); I != E; ++I) {
    if (I->getName() == "llvm.global.annotations") {
       Value *V = cast<Value>(I->getOperand(0));
        errs()<<"\n "<<*(V)<<"\n";
        errs()<<"\n "<<*(V->getType())<<"\n";

结果：

  [1 x { i8*, i8*, i8*, i32 }] [{ i8*, i8*, i8*, i32 } { i8* bitcast (i32* @f to i8*), i8* getelementptr inbounds ([3 x i8]* @.str, i32 0, i32 0), i8* getelementptr inbounds ([9 x i8]* @.str1, i32 0, i32 0), i32 18 }]

 [1 x { i8*, i8*, i8*, i32 }]

2.

errs()<<"\n "<<(V->getValueID())<<"\n";
if(V->getValueID() == Value::ConstantArrayVal) {
            ConstantArray *ca = (ConstantArray *)V;
            errs()<<"\n "<<(ca[0])<<"\n";  }

结果：

[1 x { i8*, i8*, i8*, i32 }] [{ i8*, i8*, i8*, i32 } { i8* bitcast (i32* @f to i8*), i8* getelementptr inbounds ([3 x i8]* @.str, i32 0, i32 0), i8* getelementptr inbounds ([9 x i8]* @.str1, i32 0, i32 0), i32 18 }]

欢迎任何帮助！谢谢 ！

Answer 1

如果您这样做，请使用runOnModule（）而不是runOnFunction（）。或者，您可以使用该模块。 llvm.global.annotations是在函数外部定义的。里面做的事情如下：

for (Module::global_iterator I = F.global_begin(), E = F.global_end(); I != E; ++I) {

if (I->getName() == "llvm.global.annotations")
{
    errs()<<"\nllvm.global.annotations\n";
    //1. find out what global variable is by "parsing" the IR
    //2. get through the module till you find a load @f 
    //3. you can add metadata to the load function and you can easily get the metadata from the normal pass
}

} 

Answer 2

我解决了我将整个带注释的表达式转换为Value *。然后，为了避免丑陋的东西，如getAsString（），我检查V->getValueID() == Value::ConstantArrayVal是否将它投射到ConstantArray。因为它只包含数组[0]，所以我将array0> getOperand（0）转换为ConstantStruct。因此，从ConstantStruct你可以得到所有四个操作数。现在要做的只是从每个字段获取@ f，@ str的名称。这是由ConstantStruct->getOperand(0)->getOperand(0)完成的。

Answer 3

相当晚的答案，但谷歌带领我到这里，我认为提供完整的LLVM传递，发现自由文本注释将是有帮助的。此LLVM传递仅检测用__attribute标记的函数（（annotate（“someFreeTextAnnotation”）））。代码如下：

#include "llvm/Pass.h"
#include "llvm/IR/Function.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Constants.h"
#include <set>

using namespace llvm;
const char *AnnotationString = "someFreeTextAnnotation";

namespace {
struct Hello : public FunctionPass {
    static char ID;
    Hello() : FunctionPass(ID) {}
    std::set<Function*> annotFuncs;

    virtual bool doInitialization(Module &M)override{
        getAnnotatedFunctions(&M);
        return false;
    }
    bool shouldInstrumentFunc(Function &F){
        return annotFuncs.find(&F)!=annotFuncs.end();
    }
    void getAnnotatedFunctions(Module *M){
        for (Module::global_iterator I = M->global_begin(),
                E = M->global_end();
                I != E;
                ++I) {

            if (I->getName() == "llvm.global.annotations") {
                ConstantArray *CA = dyn_cast<ConstantArray>(I->getOperand(0));
                for(auto OI = CA->op_begin(); OI != CA->op_end(); ++OI){
                    ConstantStruct *CS = dyn_cast<ConstantStruct>(OI->get());
                    Function *FUNC = dyn_cast<Function>(CS->getOperand(0)->getOperand(0));
                    GlobalVariable *AnnotationGL = dyn_cast<GlobalVariable>(CS->getOperand(1)->getOperand(0));
                    StringRef annotation = dyn_cast<ConstantDataArray>(AnnotationGL->getInitializer())->getAsCString();
                    if(annotation.compare(AnnotationString)==0){
                        annotFuncs.insert(FUNC);
                        //errs() << "Found annotated function " << FUNC->getName()<<"\n";
                    }
                }
            }
        }
    }

    bool runOnFunction(Function &F) override {
        if(shouldInstrumentFunc(F)==false)
            return false;
        errs() << "Instrumenting " << F.getName() << "\n";

        return false;
    }
}; // end of struct Hello
}  // end of anonymous namespace

char Hello::ID = 0;
static RegisterPass<Hello> X("hello", "Discover annotation attribute",
        false /* Only looks at CFG */,
        false /* Analysis Pass */);